Discovery images of the supernova 2016gkg, obtained by amateur astronomer Victor Buso on September 20, 2016. The supernova becomes visible as a faint but rapidly brightening object to the south of the host galaxy, the spiral NGC 613. |
Víctor Buso and Gastón Folatelli

On September 20, 2016, the Argentine amateur astronomer was trying out a new camera he'd affixed to his 16-inch (41 centimeters) telescope. He took some shots of the spiral galaxy NGC 613 — which lies about 80 million light-years from Earth, in the southern constellation Sculptor — and spotted something interesting: a brightening pinprick of light near the end of a spiral arm.

Astronomers at the Astrophysics Institute of La Plata, just outside Buenos Aires, quickly got wind of the find. They fielded an international team that began studying the light source with bigger and more powerful scopes, both on the ground and in space, less than a day later. [Supernova Photos: Great Images of Star Explosions]

The researchers determined that Buso had imaged the "shock breakout" phase of a supernova — the first burst of visible light from an exploding star — according to a new study.

Nobody had ever captured this elusive event before. In getting his random lucky shots, Buso had bucked odds of 1 in 10 million, or perhaps even 1 in 100 million, study team members said.

"It's like winning the cosmic lottery," said study co-author Alex Filippenko, an astronomer at the University of California, Berkeley who helped observe the newborn supernova using the Lick and Keck observatories in California and Hawaii, respectively.

"Buso's data are exceptional," Filippenko added in a statement from UC Berkeley. "This is an outstanding example of a partnership between amateur and professional astronomers."

supernova — a once-massive star that exploded after collapsing rapidly under the force of its own immense gravity.

Modeling work performed by the study team suggests that the dead star was originally about 20 times more massive than our sun. But, over the years, it had a lot of mass siphoned away, likely by a companion star, and probably harbored about five solar masses when it exploded, researchers said.

A powerful pressure wave from that explosion heated up the dead star's surface gas, causing it to brighten and emit light — the "shock breakout" that Buso captured.

"Professional astronomers have long been searching for such an event," Filippenko said. "Observations of stars in the first moments they begin exploding provide information that cannot be directly obtained in any other way."

The study, which was led by Melina Bersten of the Astrophysics Institute of La Plata, was published online today (Feb. 21) in the journal Nature.